<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>el挂载点</title>
</head>

<body>
    <div id="app" class="app">
        {{message}}
    </div>
    <!-- 开发环境版本，包含了有帮助的命令行警告 -->
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
    <script>
        var app = new Vue({
            // el: "#app",
            // el:".app",
            el: "div",
            data: {
                message: " This is a test ! 2"
            }
        })
    </script>
</body>

</html>